1. Field of the Invention
The present invention relates to a polarizing plate used for transmitting-type, reflecting-type and semitransparent reflecting-type liquid crystal displays (LCDs). In particular, the invention relates to (1) a polarizing plate used for a large liquid crystal display or a high contrast liquid crystal display, and (2) a polarizing plate used for a liquid crystal display in which a LCD module itself is thinned and lightened.
2. Description of the Prior Art
Recently, demand for LCDs used for, for example, personal computers has increased sharply. Application for LCDs has also broadened. Recently, such LCDs are used for monitoring as well.
A polarizing plate used for a LCD is manufactured, for example, by a method including steps of: dyeing a polyvinyl alcohol (PVA) film with dichroic iodine or a dichroic dyestuff; crosslinking the film with boric acid, borax, or the like; stretching the film uniaxially, followed by drying the film and sticking it to a protective layer such as a triacetylcellulose (TAC) film. The respective steps of dyeing, crosslinking and stretching are not necessarily carried out separately and can be carried out simultaneously. Furthermore, there is no limitation on the order of the steps.
In recent years, the size of LCDs has become larger, demands for high contrast have increased and higher quality polarizing plates have been required. Furthermore, both in small-size LCDs and large-size LCDs, thinning and lightening of the LCD itself are demanded. Recently, in particular, as liquid crystal displays have become larger and larger, the liquid crystal itself is becoming larger, while thinning and lightening of mobile displays are being advanced.
However, if the thickness of a polarizer, a protective layer and a pressure sensitive adhesive layer of the polarizing plate are simply reduced in order to meet the above-mentioned demands, such as thinning or lightening, when the polarizing plate is attached to a glass plate of a liquid crystal cell, there arise some problems in that the polarizing plate is peeled off from the glass plate or foams are generated or warping occurs in the glass plate.
In one aspect, the present invention relates to a thin polarizing plate and a thin and light liquid crystal display using a thin polarizing plate. By thinning the polarizing plate, the weight of the large-size liquid crystal display may be prevented from increasing due to the increase in size of the liquid crystal display and miniaturization and lightening of mobile liquid crystal displays is achieved.
In embodiments of the present invention, a thin polarizing plate includes a polarizer, a protective layer formed on at least one side of the polarizer, and a pressure sensitive adhesive layer formed on the protective layer, wherein the thickness A of the polarizer, the thickness B of the protective layer, and the modulus of elasticity C of a pressure sensitive adhesive in the pressure sensitive adhesive layer, numerical value 1 and numerical value 2 satisfy the following relationships:
(numerical value 1)=B/A less than 2.0
(numerical value 2)=(numerical value 1)/C less than 20.
In some embodiments of the present invention, it is preferable that the numeral value 2 is 12 or less.
In some embodiments of the present invention, a reflector or a transreflector may be attached to the polarizing plate.
In some embodiments of the present invention, a retardation plate or a xcex plate may be attached to the polarizing plate.
In some embodiments of the present invention, a viewing angle compensating film may be attached to the polarizing plate.
In some embodiments of the present invention, a brightness-enhanced film may be attached to the polarizing plate.
In some embodiments of the present invention, the polarizing plate is subjected to an anti-glare treatment.
In some embodiments of the present invention, a liquid crystal display uses the polarizing plate in accordance with an embodiment described above on at least one side of a liquid crystal cell.